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The life expectancy of HIV-infected patients treated with highly active antiretroviral therapy (HAART) has increased and now approaches that of the general population, while also the definition of AIDS has lost most of its epidemiological and clinical significance, due to the immune recovery obtained by large-scale administration of potent antiretroviral combinations. The prolonged survival of subjects with HIV infection, and the late recognition of patients with occult disease, will contribute to a progressive increase in disease incidence in patients aged 50-60 years or more in the near future. Unfortunately, the large majority of therapeutic trials addressed to assess and compare novel antiretroviral molecules and associations, as well as studies regarding antimicrobial chemotherapy of prophylaxis of AIDS-related opportunistic infections, have just advanced age and/or underlying chronic disorders (i.e. liver or kidney failure) among main exclusion criteria, or do not allow the extrapolation of data regarding older subjects, compared with younger ones. The limited data available until now show that antiretroviral therapy has a similar virological efficacy in the elderly compared with younger patients. However, immune reconstitution is often slower and blunted according to age progression, although some well-designed studies have shown that the thymic function (which controls most quantitative and functional immune recovery) can be preserved in adults and even in advanced age. When facing older subjects, the Infectious Disease specialist has to pay careful attention to any chronic end-organ disorders, all possible pharmacological interactions, and overwhelming toxicity due to underlying drug therapies: all these issues may significantly interfere with HAART efficacy, patients' adherence to prescribed treatments, and frequency and severity of untoward events. Guidelines for antiretroviral therapy and treatment and prophylaxis of AIDS-associated illnesses should be appropriately updated, given the novel features due to the emerging increase in the mean age of the HIV-infected patient population.

In order to provide an updated balance of the evolution of the natural history of HIV infection, the major clinical end-points of disease morbidity and mortality were compared with the progressively increasing use of highly active antiretroviral therapy (HAART), in a cohort of patients followed by our tertiary care centre in an eight-year period including both the pre-HAART and the HAART era. Although direct expenditures for antiretroviral agents reached even 99.8% of overall costs related to drugs and blood derivatives at our entire unit in the year 2000, a clear shift towards outpatient assistance of HIV infection was realized during recent years, leading to an increased and greatly varied spectrum of infectious diseases hospitalized at our inpatient and Day-Hospital units. Due to the significant reduction of inpatient expenditures, even the elevated costs of management of HIV disease based on HAART and periodic virological and immunological monitoring are expected to remain cost-effective, at least during the next few years.

The administration of antiretroviral compounds to our cohort of HIV-infected patients was assessed since 1994, on the ground of some epidemiological, clinical, and therapeutic variables. During the six-year study period, a significant increase of mean prescription rate of overall anti-HIV agents was observed, with a nearly 10-fold rise of mean prescribed daily doses per 1,000 patients-year. In particular, lamivudine and indinavir represented the most frequently administered drugs, among nucleoside analogues and protease inhibitors, respectively. A significant increase of the percentage of HIV-infected patients undergoing combined antiretroviral therapy (79.3% in 1999), and the mean number of drugs prescribed per patient (3.02 in 1999), was concurrently detected. The progressive changes of antiretroviral therapy guidelines were responsible for a nearly 16-fold increase of expenditures directly related to antiretroviral drug administration in 1999 compared with 1994 (with over 41% of costs related to protease inhibitors). On the other hand, a substantial modification of HIV disease evolution occurred in our patient cohort in terms of absolute morbidity and mortality figures, as expressed by a drop of notified AIDS cases and AIDS-related deaths ranging from 2.5 to 5 times, during the considered period.